Method of making antifuse structures using implantation of both neutral and dopant species

ABSTRACT

An antifuse structure includes a first electrode, a layer of enhanced amorphous silicon over the first electrode, and a second electrode over the layer of enhanced amorphous silicon. The layer of enhanced amorphous silicon is formed by an ion-implantation of a neutral species and a dopant species into a deposited layer of amorphous silicon, such that the antifuse structure will have a stable conductive link in a programmed state and such that it will be less susceptible to off-state leakage in an unprogrammed state. A method for making an antifuse structure includes forming a lower electrode, depositing an amorphous silicon layer over the lower electrode, ion-implanting a neutral species and a dopant species into the amorphous silicon layer, and forming an upper electrode over the amorphous silicon layer.

BACKGROUND OF THE INVENTION

The present invention relates generally to electronic integrated circuit(IC) technology. More particularly, the invention relates toelectrically programmable antifuse structures.

Antifuses can be used to selectively couple together ("program") logicelements of a field programmable gate array (FPGA) to performuser-defined functions. Alternatively, antifuses can serve as memoryelements of a programmable read-only memory (PROM). Antifuses have theadvantageous feature of being small in size, allowing a large number ofthe antifuses to be provided on a single device, and thereby providingthe capability of making a great number of interconnections or storing alarge amount of information . Antifuses and methods for making antifusesare described in U.S. Pat. Nos. 5,120,679, 5,290,734, and 5,328,868, thedisclosures of which are incorporated herein by reference.

Antifuses include a material which initially has a high resistance("unprogrammed" or "off" or "0" state) but which can be converted into alow resistance material ("programmed" or "on" or "1" state) by theapplication of a programming voltage. Programmed antifuses canselectively couple together logic elements in an FPGA, and thecombination of programmed and unprogrammed antifuses can serve as PROMmemory elements.

FIG. 1 shows a conventional metal electrode amorphous silicon antifuse10 which includes substrate 12, metal bottom electrode 14, amorphoussilicon (a-Si) layer 16, intermetal oxide layer 18, via hole 20, andmetal top electrode 22. Substrate 12 is typically a silicon wafer,electrodes 14 and 22 are typically a TiW, Al, TiW sandwich, and oxidelayer 18 is typically SiO₂. The formation of these layers are well knownto those skilled in the art. Antifuse 10 may be programmed by applying asufficiently large voltage (e.g. 15 volts dc) to top electrode 22 whilebottom electrode 14 is grounded, or vice versa.

Metal electrode amorphous silicon antifuses are typically manufacturedusing amorphous silicon deposition processes to form deposited amorphoussilicon films of the antifuses. Typical amorphous silicon depositionprocesses include chemical vapor deposition (CVD), plasma enhancedchemical vapor deposition (PECVD), and low pressure chemical vapordeposition (LPCVD). Relatively low temperatures are used in theseprocesses (about 400° C. for CVD and PECVD, and about 600°-700° C. forLPCVD so as to avoid damage to logic devices, such as CMOS transistors,formed previously in the substrate over which the antifuses are formed.

FIG. 1a shows amorphous silicon layer 16 as deposited with lowtemperature amorphous silicon deposition processes. Amorphous siliconlayer 16 created by conventional processes are believed to includerelatively conductive polysilicon regions or "islands" 26 within thea-Si matrix of silicon layer 16. Polysilicon islands 26 can lead to aphenomenon known as "off-state leakage" in which an electricallyconductive path 28 may be formed in unprogrammed antifuse 10 betweenupper electrode 22 and lower electrode 14 by jumping from onepolysilicon island 26 to another through silicon layer 16.

FIG. 1b illustrates amorphous silicon layer 16 after antifuse 10 isprogrammed. One or more conducting filaments 24 are believed to beformed by the electro-migration of electrode material into the amorphoussilicon 16. A description of conducting filaments in programmed antifusedevices may be found in the paper "Conducting Filament of the ProgrammedMetal Electrode Amorphous Silicon Antifuse", K. Gordon and R. Wong, IEDMTech. Dig., p. 27, Dec. 1993, incorporated herein by reference.

A problem often encountered with conventional antifuses is known asdeprogramming, in which after an antifuse has been subjected to aprogramming voltage believed to be sufficient to program the antifuse toan "on" state, it is later found that such antifuse is instead in anunprogrammed "off" state. Deprogramming refers to either the situationin which no adequately conducting filament has been formed by theapplication of a programming voltage to the antifuse, or to a tendencyof the resistance of a weakly "programmed" antifuse to increase withtime such that it is no longer adequately conductive. Adequatelyprogrammed antifuses should remain it their low resistance states inorder to provide reliable operation, for example, of the circuit inwhich they are incorporated.

It is apparent from the foregoing that what is needed is an antifusestructure which reliably remains conductive ("on") after it has beenprogrammed and which reliably remains nonconductive ("off") if it hasnot been programmed.

SUMMARY OF THE INVENTION

According to the present invention, an antifuse structure is providedwhich is less susceptible to off-state leakage than conventionalantifuse structures and which is efficiently programmable to reliablyremain in its "on" state.

In a preferred embodiment, the antifuse structure of the presentinvention includes, a first electrode, a layer of enhanced amorphoussilicon over the first electrode, and a second electrode over the layerof enhanced amorphous silicon. The layer of enhanced amorphous siliconis formed by an ion-implantation of at least one of a neutral speciesand a dopant species into a deposited layer of amorphous silicon. Anantifuse structure according to the invention will have a stableconductive link in a programmed state and it will be less susceptible tooff-state leakage in an unprogrammed state.

A method for making an antifuse structure according to the presentinvention includes forming a lower electrode, depositing an amorphoussilicon layer over the lower electrode, ion-implanting at least one of aneutral species and a dopant species into the amorphous silicon layer,and forming an upper electrode over the amorphous silicon layer. Theamorphousness of the silicon layer is enhanced by subjecting it to theneutral species implantation, which advantageously creates a highelectrical resistance between the electrodes of the antifuse in anunprogrammed state, while the dopant species implantation advantageouslyenhances the silicon layer such that a reliably stable conductive linkis more effectively formed therein between the electrodes of theantifuse during programming.

These and other advantages of the present invention will become clear tothose skilled in the art upon a study of the detailed description of theinvention and of the several figures of the drawings, wherein likereference numerals indicate like elements of the invention.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross section of a conventional metal electrode amorphoussilicon antifuse;

FIGS. 1a and 1b are enlarged views of the antifuse amorphous siliconlayer that is encircled by line 1 in FIG. 1, respectively showingunprogrammed off state leakage and a programmed conducting filament;

FIG. 2 is a flow diagram of the process of the present invention;

FIGS. 2a-2c are cross sections illustrating the manufacturing steps foran antifuse structure made in accordance with the process of FIG. 2;

FIG. 2d is a cross section illustrating one preferred embodiment of anantifuse structure made in accordance with the process of FIG. 2;

FIG. 3 is a flow diagram of one embodiment of ion implantation steps ofthe process of the present invention;

FIG. 3a-3c are cross sections illustrating the manufacturing steps foran antifuse structure made in accordance with the steps of FIG. 3;

FIG. 4 is a flow diagram of another embodiment of ion implantation stepsof the process of the present invention;

FIGS. 4a-4c are cross sections illustrating the manufacturing steps foran antifuse structure made in accordance with the steps of FIGS. 4;

FIG. 5 is a flow diagram of another embodiment of ion implantation stepsof the process of the present invention;

FIGS. 5a-5b are cross sections illustrating the manufacturing steps foran antifuse structure made in accordance with the steps of FIG. 5;

FIG. 6 is a flow diagram of still another embodiment of ion implantationsteps of the process of the present invention;

FIGS. 6a-6b are cross sections illustrating the manufacturing steps foran antifuse structure made in accordance with the steps of FIG. 6; and

FIG. 7 is a cross section illustrating an antifuse structure of thepresent invention in a programmed state with an improved conducting linkformed therein.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1, 1a and 1b were discussed with reference to the prior art. FIG.2 illustrates a basic process 30 according to the present invention formaking an improved antifuse structure. In a first step 32, a lowerelectrode is provided for the antifuse structure. This lower electrodeis preferably formed over a substrate, in which a plurality of logicdevices such as CMOS transistors have preferably been previously formed.In a step 34, a layer of amorphous silicon (a-Si) is provided over thelower electrode. The amorphous silicon layer is formed preferably byconventional amorphous silicon deposition processes such as CVD, PECVD,LPCVD, and sputter deposition processes, and preferably by theseamorphous silicon deposition processes at low-temperature which asdefined herein refers to a process temperature in the range of about400° to 500° C. for CVD and PECVD and about 600°-700° C. for LPCVD. In astep 36, an ion implantation of at least one of a neutral species and adopant species into the amorphous silicon layer deposited in step 34 isperformed. Preferably, the neutral species of ion implantation step 36is chosen from the group including Argon, Oxygen, Nitrogen, Silicon, andGermanium, while the dopant species is an n-type dopant such as, mostcommonly, Phosphorus (P+) or Arsenic (As+), or a p-type dopant such as,most commonly, Boron (B+). Finally, in a step 38, an upper electrode isprovided over at least a portion of the amorphous silicon layer whichhas been enhanced in step 36.

Ion implantation step 36 creates an "enhanced" amorphous silicon layerfor the antifuse structure of the present invention. As used herein, anenhanced amorphous silicon layer refers to a layer of amorphous silicondeposited in a conventional amorphous silicon deposition processpreferably at low-temperature, such as CVD, PECVD, and LPCVD processes,which has been subjected to an ion implantation of at least one of aneutral species and a dopant species. The neutral species ionimplantation creates an enhanced amorphous silicon layer which has ahigher degree of amorphousness than the deposited amorphous siliconlayer, thereby to decrease the presence of polysilicon regions andminimize the occurrence of off-state leakage of the unprogrammedantifuse structure. The dopant species ion implantation creates anenhanced amorphous silicon layer for an antifuse structure which permitsa decisive and stable conducting link to be formed upon programming,thereby to ensure that the antifuse structure has been adequately andreliably programmed.

Preferably, step 34 provides a layer of amorphous silicon which isdeposited with a thickness between about 400-2000 Å, while step 36includes implanting Argon with an implant energy between about 20-80 keVand an implant density of about 1×10¹² -1×10¹⁶ ions cm⁻². Even morepreferably, step 34 provides a layer of amorphous silicon which isdeposited with a thickness between about 1150-1350 Å, while step 36includes implanting Argon with an implant energy between about 25-65 keVand an implant density of about 1×10¹⁵ -1×10¹⁶ ions cm⁻². Preferably,step 34 provides a layer of amorphous silicon which is deposited with athickness of about 1250 Å, while step 36 includes implanting Argon withan implant energy of about 47 keV and an implant density of about 5×10¹⁵ions cm⁻².

According to the invention, the following ranges are employed in ann-type dopant ion implantation for step 36. Preferably, step 34 providesa layer of amorphous silicon which is deposited with a thickness betweenabout 400-2000 Å, while step 36 includes implanting Phosphorous with animplant energy between about 30-40 keV and an implant density of about1×10¹³ -1×10¹⁶ ions cm⁻². Also preferably, step 34 provides a layer ofamorphous silicon which is deposited with a thickness between about1150-1350 Å, while step 36 includes implanting Phosphorous with animplant energy between about 20-60 keV and an implant density of about1×10¹²⁻¹×10¹⁴ ions cm⁻². Preferably, step 34 provides a layer ofamorphous silicon which is deposited with a thickness of about 1250 Å,while step 36 includes implanting Phosphorous with an implant energy ofabout 37 keV and an implant density of about 5×10¹⁴ ions cm⁻².

According to the invention, the following ranges are employed in ap-type dopant ion implantation for step 36. Preferably, step 34 providesa layer of amorphous silicon which is deposited with a thickness betweenabout 400-2000 Å, while step 36 includes implanting Boron with animplant energy between about 40-80 keV and an implant density of about1×10¹³ -1×10¹⁶ ions cm⁻². Even more preferably, step 34 provides a layerof amorphous silicon which is deposited with a thickness between about1150-1350 Å, while step 36 includes implanting Boron with an implantenergy between about 45-90 keV and an implant density of about 1×10¹²-1×10¹⁴ ions cm³¹ 2. According to a preferred embodiment of the presentinvention, step 34 provides a layer of amorphous silicon which isdeposited with a thickness of about 1250 Å, while step 36 includesimplanting Boron with an implant energy of about 67 keV and an implantdensity of about 5×10¹⁴ ions cm⁻².

As described previously, step 36 includes an ion implantation of atleast one of a neutral species and a dopant species into the amorphoussilicon layer deposited in step 34. Accordingly in the preferredembodiments of the present invention, step 36 may include any singleneutral species ion implantation or dopant species ion implantation inthe ranges given above, or any combination of neutral species and dopantspecies ion implantations in the ranges given above. A single neutralion implantation provides an enhanced amorphous silicon layer which hasa higher degree of amorphousness than the deposited amorphous siliconlayer, thereby to decrease the presence of polysilicon regions andminimize the occurrence of off-state leakage of the unprogrammedantifuse structure. A single dopant species ion implantation provides anenhanced amorphous silicon layer for an antifuse structure which permitsa decisive and stable conducting link to be formed upon programming,thereby to ensure that the antifuse structure has been adequately andreliably programmed. In a preferred embodiment, a combined neutral ionimplantation and dopant species ion implantation provides an enhancedamorphous silicon layer which both minimizes off-state leakage andensures adequate and reliable programming.

FIGS. 2a-2c sequentially illustrate the structures produced by therespective steps of process 30. In FIG. 2a, a first electricallyconductive electrode 40 is arranged over a substrate 42, and anamorphous silicon layer 44 is arranged over first electrode 40 such thata first surface of amorphous silicon layer 44 is in electrical contactwith first electrode 40. Substrate 42 is preferably a silicon wafer, andfirst electrode 40 is preferably made of metal and preferably formed bya sputter deposition process. Even more preferably, first electrode 40is a TiW, Al, TiW three layer sandwich.

In FIG. 2b, a layer of enhanced amorphous silicon 46 is arranged overfirst electrode 40. Enhanced amorphous silicon layer 46 is formed by anion-implantation 48 of at least one of a neutral species and a dopantspecies into deposited layer of amorphous silicon 44. A first surface ofenhanced amorphous silicon layer 46 is in electrical contact with firstelectrode 40. In FIG. 2c, a second electrically conductive electrode 50is arranged in electrical contact with a second surface of enhancedamorphous silicon layer 46 opposite the first surface thereof.Preferably, second electrode 50 is made of metal, and preferably formedby a sputter deposition process. Even more preferably, second electrodeis Titanium-Tungsten (TiW). First electrode 40, enhanced amorphoussilicon layer 46, and second electrode 50 together form an antifusestructure in accordance with the present invention.

In a preferred embodiment, process 30 further includes a step of formingan insulator or dielectric layer over the amorphous silicon layer, suchthat the dielectric layer includes a via hole aligned with a portion ofthe amorphous silicon layer. In this case, step 38 includes forming theupper electrode in contact with the amorphous silicon layer through thevia hole of the dielectric layer. FIG. 2d shows an antifuse structuremanufactured according to this preferred embodiment, in which adielectric layer 52, including a via hole 54, is formed in contact withenhanced amorphous silicon layer 46. Second electrode 50 contactsenhanced amorphous silicon layer 46 through via hole 54. Preferably,dielectric layer 52 with via hole 54 is formed in a manner well known tothose skilled in the art, by depositing a layer of SiO₂ in an LPCVD orPECVD deposition process, and then patterning (masking and etching) theSiO₂ layer to form via hole 54.

Dielectric layer 52 with via hole 54 may be formed before or afteramorphous silicon layer 46 is enhanced by ion implantation. Dielectriclayer 52 acts as a mask during any subsequent ion implantation whichtherefore occurs substantially only at the portion of amorphous siliconlayer 46 which is aligned with via hole 54.

Several preferred methods of forming an antifuse structure according tothe invention, and in particular preferred methods of carrying oution-implantation step 36, will now be described. In FIG. 3, oneembodiment 36a of ion-implantation step 36 includes a first step 60 ofion-implanting the deposited amorphous silicon layer with a neutralspecies, a subsequent step 62 of forming and patterning an insulatorlayer with a via over a portion of the amorphous silicon layer, and asubsequent step 64 of ion-implanting the amorphous silicon layer with adopant species through the via of the insulator layer.

FIGS. 3a-3c sequentially illustrate the structures produced by severalpreferred steps of process 36a. In FIG. 3a, an enhanced amorphoussilicon layer 46a is formed by a neutral species ion-implantation 48a ofthe deposited amorphous silicon layer. In FIG. 3b, dielectric layer 52with via hole 54 is formed over enhanced amorphous silicon layer 46a. InFIG. 3c, an enhanced amorphous silicon layer 46b is formed by a dopantspecies ion-implantation 48b through via hole 54. As an end result,enhanced amorphous silicon layer 46b therefore includes exclusivelyneutral species implanted portions 56 aligned substantially belowdielectric layer 52 and a neutral species and dopant species implantedportion 58 aligned substantially with via hole 54.

In FIG. 4, another embodiment 36b of ion-implantation step 36 includes afirst step 70 of ion-implanting the deposited amorphous silicon layerwith a dopant species, a subsequent step 72 of forming and patterning aninsulator layer with a via over a portion of the amorphous siliconlayer, and a subsequent step 74 of ion-implanting the amorphous siliconlayer with a neutral species through the via of the insulator layer.

FIGS. 4a-4c sequentially illustrate the structures produced by somepreferred steps of process 36b. In FIG. 4a, an enhanced amorphoussilicon layer 46c is formed by dopant species ion-implantation 48b ofthe deposited amorphous silicon layer. In FIG. 4b, dielectric layer 52with via hole 54 is formed over enhanced amorphous silicon layer 46c. InFIG. 3c, an enhanced amorphous silicon layer 46d is formed by neutralspecies ion-implantation 48a through via hole 54. As an end result,enhanced amorphous silicon layer 46d therefore includes neutral speciesand dopant species implanted portion 58 aligned substantially with viahole 54, and exclusively dopant species implanted portions 76 alignedsubstantially below dielectric layer 52.

In FIG. 5, another embodiment 36c of ion-implantation step 36 includes afirst step 80 of ion-implanting the deposited amorphous silicon layerwith both a dopant species and a neutral species, and a subsequent step82 of forming and patterning an insulator layer with a via over aportion of the amorphous silicon layer.

FIGS. 5a-5b sequentially illustrate the structures produced by somepreferred steps of process 36c. In FIG. 5a, an enhanced amorphoussilicon layer 46e is formed by dopant species ion-implantation 48b andby neutral species ion-implantation 48a of the deposited amorphoussilicon layer. In FIG. 5b, dielectric layer 52 with via hole 54 isformed over enhanced amorphous silicon layer 46b. Enhanced amorphoussilicon layer 46e therefore includes neutral species and dopant speciesimplanted portion 58 aligned substantially with via hole 54 and belowdielectric layer 52.

In FIG. 6, another embodiment 36d of ion-implantation step 36 includes afirst step 90 of forming and patterning an insulator layer with a viaover a portion of the deposited amorphous silicon layer, and asubsequent step 92 of ion-implanting the deposited amorphous siliconlayer with both a dopant species and a neutral species through the via.

FIGS. 6a-6b illustrate the structures produced by some preferred stepsof process 36c. In FIG. 6a, dielectric layer 52 with via hole 54 isformed over deposited amorphous silicon layer 46. In FIG. 6b, anenhanced amorphous silicon layer 46f is formed by dopant speciesion-implantation 48b and by neutral species ion-implantation 48a of thedeposited amorphous silicon layer through via 54. Enhanced amorphoussilicon layer 46f therefore includes neutral species and dopant speciesimplanted portion 58 aligned substantially with via hole 54, andnon-enhanced amorphous silicon portions 94 aligned substantially belowdielectric layer 52.

It will be noted that all of enhanced amorphous silicon layers 46b, 46d,46e, and 46f of the previously described preferred antifuse structuresinclude a neutral species and dopant species implanted portion 58aligned substantially with via hole 54 of dielectric layer 52. An upperelectrode may be formed, for example in a manner similar to theformation of second electrically conductive electrode 50 of the antifusestructure shown in FIG. 2d, such that it contacts neutral species anddopant species implanted portion 58 through via hole 54.

Neutral species ion-implantation 48a and dopant species ion-implantation48b may be carried out according to the implant energy and densityranges for the amorphous silicon layer thickness ranges given above withregard respectively to ion-implantation step 36 and deposition step 34.

Ion implantation step 36a of FIG. 3 is a preferred embodiment of thepresent invention. Neutral species ion-implanting step 60, prior toinsulator layer forming, creates an enhanced amorphous silicon layerwhich protects against off-state leakage at both the via and at portionsof the enhanced layer positioned beneath the insulator layer (refer toFIG. 3c showing neutral species implanted portions 56 alignedsubstantially below dielectric layer 52). Ion implantation step 64further creates an enhanced amorphous silicon layer which facilitatesreliable conducting link formation particularly at the insulator layervia where it is most needed.

In FIG. 7, an antifuse structure of the present invention in aprogrammed state is illustrated with an improved conducting linkformation. Upon programming by applying a sufficient voltage (e.g. 15volts dc) an improved conducting link 100 is formed in portion 58, whichhas been ion implanted with a dopant species. Conducting link 100includes a metal silicide filament 102, believed to be formed by theelectromigration of electrode material of electrodes 40 and 50 intoenhanced amorphous silicon layer 46b, and doped polysilicon region 104,believed to be formed adjacent filament 102 by the heat generated duringformation of filament 102. Conducting link 100 may be seen as anexpanded conducting path which includes the parallel conducting paths offilament 102 and polysilicon region 104, which together ensure that theantifuse structure is adequately and reliably programmed.

While this invention has been described in terms of several preferredembodiments, it is contemplated that various alterations andpermutations thereof will become apparent to those skilled in the art.It is therefore intended that the appended claims include all suchalterations and permutations as fall within the true spirit and scope ofthe present invention.

What is claimed is:
 1. A method of making an antifuse structurecomprising the steps of:forming a substantially planar lower electrode;depositing a substantially planar amorphous silicon layer over saidlower electrode such that a first surface of said amorphous siliconlayer thereof is in electrical contact with said lower electrode,wherein said amorphous silicon layer is deposited over said lowerelectrode such that said amorphous silicon layer is in physical contactwith substantially only said lower electrode; ion-implanting both aneutral species and a dopant species into at least a portion of a secondsurface of said amorphous silicon layer which opposes said first surfaceof said amorphous silicon layer; and forming an upper electrode oversaid amorphous silicon layer in electrical contact at least with saidportion of said second surface after said portion of said second surfaceis ion-implanted with both said neutral species and said dopant species.2. A method of making an antifuse structure according to claim 1 whereinsaid neutral species is chosen from the group consisting essentially ofArgon, Oxygen, Nitrogen, Silicon, and Germanium, and wherein said dopantspecies is one of an n-type dopant and a p-type dopant.
 3. A method ofmaking an antifuse structure according to claim 1 wherein said amorphoussilicon layer is deposited with a thickness between about 400-2000 Å,and wherein said step of ion-implanting includes implanting Argon withan implant energy between about 20-λkeV and an implant density of about1×10¹² -1×10¹⁶ ions cm⁻².
 4. A method of making an antifuse structureaccording to claim 1 wherein said amorphous silicon layer is depositedwith a thickness between about 1150-1350 Å, and wherein said step ofion-implanting includes implanting Argon with an implant energy betweenabout 25-γkeV and an implant density of about 1×10¹⁵ -1×10¹⁶ ions cm⁻².5. A method of making an antifuse structure according to claim 1 whereinsaid amorphous silicon layer is deposited with a thickness of about 1250Å, and wherein said step of ion-implanting includes implanting Argonwith an implant energy of about 47 keV and an implant density of about5×10¹⁵ ions cm⁻².
 6. A method of making an antifuse structure accordingto claim 1 wherein said amorphous silicon layer is deposited with athickness between about 400-2000 Å, and wherein said step ofion-implanting includes implanting Phosphorous with an implant energybetween about 20-80 keV and an implant density of about 1×10¹² -1×10¹⁶ions cm⁻².
 7. A method of making an antifuse structure according toclaim 1 wherein said amorphous silicon layer is deposited with athickness between about 1150-1350 Å, and wherein said step of ionimplantation includes implanting Phosphorous with an implant energybetween about 20-60 keV and an implant density of about 1×10¹² -1×10¹⁴ions cm⁻².
 8. A method of making an antifuse structure according toclaim 1 wherein said amorphous silicon layer is deposited with athickness of about 1250 Å, and wherein said step of ion-implantingincludes implanting Phosphorous with an implant energy of about 37 keVand an implant density of about 5×10¹⁴ ions cm⁻².
 9. A method of makingan antifuse structure according to claim 1 wherein said amorphoussilicon layer is deposited with a thickness between about 400-2000 Å,and wherein said step of ion-implanting includes implanting Boron withan implant energy between about 20-80 keV and an implant density ofabout 1×10¹² -1×10¹⁶ ions cm⁻².
 10. A method of making an antifusestructure according to claim 1 wherein said amorphous silicon layer isdeposited with a thickness between about 1150-1350 Å, and wherein saidstep of ion implantation includes implanting Boron with an implantenergy between about 45-90 keV and an implant density of about 1×10¹²-1×10¹⁴ ions cm⁻².
 11. A method of making an antifuse structureaccording to claim 1 wherein said amorphous silicon layer is depositedwith a thickness of about 1250 Å, and wherein said step ofion-implanting includes implanting Boron with an implant energy of about67 keV and an implant density of about 5×10¹⁴ ions cm⁻².
 12. A method ofmaking an antifuse structure according to claim 1 further comprising thestep of:forming a dielectric layer including a via hole aligned withsaid portion of said second surface; and wherein said step of forming anupper electrode over said amorphous silicon layer includes forming saidupper electrode in contact with said portion of said second surfacethrough said via hole in said dielectric layer.
 13. A method of makingan antifuse structure according to claim 12 wherein said step ofion-implanting includes implanting said neutral species before said stepof forming a dielectric layer and implanting said dopant species throughsaid via hole after said step of forming a dielectric layer and beforesaid step of forming said upper electrode.
 14. A method of making anantifuse structure according to claim 12 wherein said step ofion-implanting includes implanting said dopant species before said stepof forming a dielectric layer and implanting said neutral speciesthrough said via hole after said step of forming a dielectric layer andbefore said step of forming said upper electrode.
 15. A method of makingan antifuse structure according to claim 12 wherein said step ofion-implanting includes implanting both said neutral species and saiddopant species before said step of forming a dielectric layer.
 16. Amethod of making an antifuse structure according to claim 12 whereinsaid step of ion-implanting includes implanting both said neutralspecies and said dopant species through said via hole after said step offorming a dielectric layer and before said step of forming said upperelectrode.
 17. A method of making an antifuse structure according toclaim 1 wherein forming the lower electrode includes forming a metallower electrode and forming the upper electrode includes forming a metalupper electrode.
 18. A method of making an antifuse structure accordingto claim 17 further including a step of providing a substrate over whichsaid lower electrode is formed.
 19. A method of making an antifusestructure according to claim 18 including providing a substrate having aplurality of logic devices arranged therein.